How are steroids able to cross cell membranes and enter cells?
A) Steroids and cell membranes both contain receptor proteins.
B) Steroids are able to pass through the phospholipid bilayer.
C) Steroids can diffuse through open channel proteins in the membrane.
D) Steroids move through cell membranes by osmosis.
Answer: B) Steroids are able to pass through the phospholipid bilayer.
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Your father is heterozygous for a recessive disorder. You know your mom has two "good" alleles
What is the probability that you will have the disorder?
a. 0% b. 25% c. 50% d. 75% e. 100%
Which of the following have young which feed on milk?
A. placental mammals and marsupials B. monotremes C. placental mammals, marsupials, and monotremes D. placental mammals E. marsupials
The microbial death rate is (constant/nonlinear/variable) over time
What will be an ideal response?
Ras is a GTP-binding protein that is often defective in cancer cells. A signal from a growth factor through a receptor tyrosine kinase often stimulates normal cells to divide
When the receptor tyrosine kinase binds the growth factor, Ras is stimulated to bind GTP. Ras in turn activates proteins that promote cell proliferation. A common mutation in cancerous cells causes Ras to behave as though it were bound to GTP all the time. A. Why is this mutation advantageous to cancerous cells? B. Your friend decides that the signaling pathway involving the Ras protein is a good target for drug design, because the Ras protein is often defective in cancer cells. Your friend designs a drug that will turn off the receptor tyrosine kinase by preventing it from dimerizing. Do you think that this drug will affect cells that have a defective Ras protein that acts as if it were always bound to GTP? Why or why not?